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Small patch of 65 plants in mature Nyssa sylvatica stand with moderate to low density of Clethra alnifolia. Close to small stream, well off trail. Gaultheria procumbens and Mitchella repens nearby but not much groundcover.

Both subsp. americanus (native to North America) and subsp. australis (introduced to North America) are found at this site, sometimes growing intermixed. In the photos the former is indicated with an “N” and the latter with an “I”. On the date I visited this site, 16 September 2019, these are the differences I observed with living stems between the two subspecies:

•Relative stem height: subsp. americanus usually shorter, subsp. australis usually taller.
•Relative stem spacing: subsp. americanus usually more dispersed, subsp. australis usually denser (rarely solitary).
•Stem breaking: subsp. americanus fibrous and hard to break off, subsp. australis often breaks off easily.
•Stem color (lower/older internodes): subsp. americanus red and often shiny, subsp. australis yellow-green and not shiny.
•Stem texture (lower/older internodes): subsp. americanus smooth, subsp. australis minutely ridged.
•Stem & leaf sheath dots: subsp. americanus often present, subsp. australis absent.
•Leaf condition: subsp. americanus has lots of senescence, subsp. australis generally are healthy.
•Margins of upper leaves near panicle: subsp. americanus finely serrated, subsp. australis coarsely serrated.
•Sterile stems more abundant than fertile: subsp. americanus yes, subsp. australis no.
•Panicle branches for panicles of similar length: subsp. americanus fewer, subsp. australis more.
•Panicle branch spacing: subsp. americanus farther, subsp. australis closer.
•Flowering status: subsp. americanus finished flowering, subsp. australis flowering.

There probably are other characteristics I overlooked that distinguish these two subspecies from each other. Perhaps these characteristics listed above hold up at other sites in North America. I don’t use leaf color to tell them apart because although some clones of subsp. australis are strongly blue-green, some clones of that subspecies are more green or yellow-green. See this observation for an illustration: https://www.inaturalist.org/observations/30610594

Observation of P. australis subsp. americanus from this location: https://www.inaturalist.org/observations/32878566

Observation of P. australis subsp. australis from this location: https://www.inaturalist.org/observations/32888630

Natural light shot of Metridium lining the walls at Burnham. The peaks of this trench seem to gather the most invertebrates as seen here (with strobe): https://www.inaturalist.org/observations/82101339
In the area pictured, the depths range from ≈21-33m. I consider this to be a world class dive. There's always a lot to observe without having to travel far from the mooring line and the trench makes for easy navigation in what would otherwise be a dark and confusing spot.

It's not often that my fieldwork results in finding a new native globally rare species to add to the flora of Massachusetts, but it happened in May. ID confirmed by Vermont moonwort expert Art Gilman, author of the New Flora of Vermont. (Arthur Haines agreed as well).

I'm assuming that this is non-native, but the red stalks, somewhat diffuse colonial pattern and limited flowering have me wanting a second opinion. The red stalks could be just a result of being submerged for most of the growing season. This is growing on the drawn-down shore of the Quabbin Reservoir, where large stands of obvious non-native stands are established. On sandy shoreline.

@wernerehl